NOTES Class 10 Science chapter 9: Light – Reflection and Refraction -2

 

Refraction of Light

Refraction is the bending of light as it passes from one medium to another with different optical densities. This change in direction is due to the change in the speed of light in different media.

Laws of Refraction (Snell's Law)

• The incident ray, the refracted ray, and the normal to the interface of two media all lie in the same plane.
• The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media (refractive index).

Refractive Index

The refractive index (n) is a measure of how much the speed of light decreases in a medium compared to a vacuum. It is given by: $n = \frac{c}{v}$ where $c$ is the speed of light in a vacuum and $v$ is the speed of light in the medium.

Refraction through a Glass Slab

When light passes through a rectangular glass slab, it undergoes refraction twice, bending towards the normal when entering the denser medium and away from the normal when exiting. The emergent ray is parallel to the incident ray but displaced sideways.

Applications of Refraction

• Lenses: Used in spectacles, cameras, microscopes, and telescopes.
• Prisms: Used in spectrometers to disperse light into its constituent colors.
• Total Internal Reflection: Used in optical fibers for communication and in periscopes.

Practical Activities

Activity with a Coin and Water

Demonstrates the refraction of light by observing the apparent displacement of a coin placed in water.

Activity with a Glass Slab

Shows the bending of light as it passes through a glass slab, illustrating the principles of refraction.

Also Read:

• MCQs on reflection of Light class 10
• Excretion MCQs
• Light: Reflection and Refraction - 1 Notes
• Light: Reflection and Refraction - 3 Notes